1. Field of the Invention
This invention relates to a guide roller assembly to be rotatably mounted on a truck frame of a crawler type vehicle for guiding a crawler belt, and also to a method of forming a guide roller for the guide roller assembly.
2. Description of the Prior Art
Generally, crawler type vehicles such as hydraulic power shovels or cranes are largely constituted by a base carrier, and an upper rotary body which is rotatably mounted on top of the base carrier. In turn, the base carrier is largely constituted by a truck frame, an idler wheel and a drive sprocket which are located at each side of the truck frame in spaced front and rear positions, and an endless crawler belt which is passed between and around the drive sprocket and the idler wheel. Provided also at each side of the truck frame, between the drive sprocket and idler wheel, is a crawler belt guide roller mechanism having a plural number of guide rollers for guiding movements of the crawler belt.
For example, as disclosed in Japanese Laid-Open Utility Model Application 1-98784, a crawler belt guide roller mechanism of this sort usually includes a truck frame, a support shaft which is fixedly supported on the truck frame, and a guide roller which is rotatably mounted on the circumference of the support shaft through a pair of bearings. Formed in an axially intermediate portion of the guide roller is a space which is filled with a lubricant oil to serve as an oil reservoir. The lubricant oil in the oil reservoir space, which is sealed by seal members at its opposite axial ends, is supplied to sliding surfaces of the support shaft and bearings for lubrication thereof.
According to the prior art, the guide rollers of this sort are normally of the so-called split type which consists of a pair of roller halves which are arranged symmetrically relative to an axial split plane. The roller halves are separately formed by hot forging, and joined together by welding axially intermediate portions.
The guide rollers of this sort are usually formed through a process which includes at least a heating step of heating the material for the roller halves to a high temperature, a forging step of press-forging the heated material with use of a die, a mechanical machining step of machining to shape the forged bodies of roller halves and forming joint portions on each one of the roller halves, and a welding step of welding the joint portions of the machined roller halves together to form the guide rollers.
In this manner, the guide roller forming process requires a large number of steps such as; heating, forging, mechanical machining and welding as mentioned above, which are necessarily reflected by a high production cost of the guide rollers mainly due to high equipment costs for the heating and forging steps.
In addition, the guide rollers, which are formed by welding together roller halves as described above, have an inherent problem that cracks are likely to develop in the welded joint portions of the guide rollers to make it difficult to operate the guide roller mechanism stably over a long period of time, for example, especially in the case of a crawler type vehicle which is driven repeatedly on severely rough and bumpy grounds over a long period of time.